Apparatus for coding or decoding intra image based on line information of reference image block

ABSTRACT

An apparatus for coding an image is provided to effectively code the image. The apparatus for coding the image includes an input image segmentation unit to segment an input image into a plurality of image blocks including a first image block and a second image block. The apparatus also includes a waveform information generation unit to select a plurality of reference pixels from among pixels included in the first image block, generate first waveform information about the first image block based on a pixel value difference between the selected plurality of reference pixels, and generate second waveform information about the second image block based on a pixel value difference between the pixels included in the second image block. The apparatus also includes a coding unit to code an image included in the second image block based on the first waveform information and the second waveform information.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 12/811,765filed on Jul. 6, 2010, which is a U.S. national stage application ofInternational Application No. PCT/KR2008/007733 filed on Dec. 29, 2008.This application claims the benefit of Korean Application Nos.10-2008-0000895 filed on Jan. 3, 2008, and 10-2008-0065510 filed on Jul.7, 2008. The entire disclosures of application Ser. No. 12/811,765,International Application No. PCT/KR2008/007733, and Korean ApplicationNos. 10-2008-0000895 and 10-2008-0065510 are incorporated herein byreference for all purposes.

TECHNICAL FIELD

The present invention relates to an apparatus for coding/decoding animage in a screen, and more particularly, to an apparatus foreffectively coding and an apparatus for decoding the effectively codedimage. This work was supported by the IT R&D program of MIC/IITA[2007-S-005-01, The Development of Rich Media Broadcasting Techniquethrough enhancement of AV codec.

BACKGROUND ART

The present communication environment is rapidly evolving, transcendingboundaries of regions and countries and fields of wired/wirelesscommunication, and this movement is bound to continue its course intothe future. In this trend, the communication environment is prepared tointegrally provide various information required by users as well asimages and voices in a real-time. Digital television systems processingthe moving image into digital data, transmitting the digital data inreal-time, and mobile communication networks receiving the digital datafor displaying the moving image being transmitted in real-time inpersonal terminals are implemented and popularized.

FIG. 1 is a block diagram illustrating a structure of an apparatus forcoding a moving image according to conventional technologies.

Both inter prediction 120 and intra prediction 121 are performed with aninput image 110. A switch 140 selects a better prediction method betweenthe inter prediction 120 and intra prediction 121. A difference imagebetween the input image 110 and a prediction image obtained from eitherthe inter prediction 120 or intra prediction 121 is entropy coded 160via discrete cosine transform (DCT) 130 and quantization 150. Also, thedifference image reconstructed in this apparatus for coding the movingimage through inverse quantization 151 and inverse DCT 131 is summedwith the prediction image obtained through the inter prediction 120 orintra prediction 121, thereby obtaining a reconstructed image. Thisreconstructed image is used for the intra prediction 121, and ade-blocking filtering 170 is performed on the reconstructed image isused for the inter prediction 120.

In such commercialization process, development of a moving imagecompression technology functions as a core factor since the moving imagecompression technology performs quantization with respect to analogimage signals, processes special digital processes such as variablelength coding, includes the processed signals in digital information andtransmits the digital information, and decodes the transmitted digitalinformation received in a terminal, thereby transmitting/receiving moreabundant information at a faster transmission speed. To enhanceefficiency of the moving image compression, intra prediction mode andinter prediction mode are provided and implemented. In particular, theintra prediction mode is a prediction method exclusively usinginformation within an image frame, without using temporal correlation.As precise prediction is performed, redundancy with an original block tobe coded is increased, and an amount of data is minimized by removingredundancy from the original block when actually transmitting, therebyenhancing the compression.

The H.264 coding standard may improve coding efficiency by using codingtools different from conventional arts. The intra prediction coding,which is one of newly used coding tools, predicts a coding target blockby using spatial correlation when coding an intra block, and exclusivelycodes a residual signal between a predicted value and an actual pixelvalue.

In such intra prediction, there are intra prediction of a 4×4 blockunit, intra prediction of an 8×8 block unit, and intra prediction of a16×16 block unit. In the intra prediction of the 4×4 block unit and theintra prediction of the 8×8 block unit, nine prediction modes areavailable. In the intra prediction of the 16×16 block unit, fourprediction modes are used. In all intra predictions, difference signalsand the information regarding the above prediction mode used in theprediction are coded together.

In the case the difference between the predicted value and the actualpixel value is small, it is possible to code a high quality image withidentical bits or it is also possible to process coding with lower bits.Therefore, an apparatus for coding an image which is capable ofgenerating prediction values with small differences to the actual pixelvalue, and an apparatus for decoding which is capable of decoding thecoded images generated from the above apparatus are required.

DISCLOSURE OF INVENTION Technical Goals

The objective of the present invention is to reduce a size of codedimages and to improve a quality of the coded images by effectivelycoding input images.

Technical Solutions

In order to achieve the objective of the present invention and resolveproblems of conventional arts, the present invention provides anapparatus for coding an image including an input image segmentation unitto segment an input image into a plurality of image blocks including afirst image block and a second image block; a waveform informationgeneration unit to select a plurality of reference pixels from amongpixels included in the first image block, generate first waveforminformation about the first image block based on a pixel valuedifference between the selected plurality of reference pixels, andgenerate second waveform information about the second image block basedon a pixel value difference between the pixels included in the secondimage block; and coding unit to code an image included in the secondimage block based on the first waveform information and second waveforminformation.

According to an aspect of the present invention, there is provides anapparatus for decoding an image including a reference block waveforminformation generation unit to generate reference block waveforminformation based on a pixel value difference between reference pixelsincluded in a reference image block; a prediction pixel value generationunit to generate a prediction pixel value based on the reference blockwaveform information and a value of a standard pixel included in thereference block; and a decoding unit to decode an image included in atarget image block based on the prediction pixel value.

According to another aspect of the present invention, there is providedan apparatus for coding an image including an input image segmentationunit to segment an input image into a plurality of image blocksincluding a reference image block and a target image block; a referenceblock waveform information generation unit to select a plurality ofreference pixels from among pixels included in the reference image blockand generate reference block waveform information based on a value ofstandard pixel included in the reference block and difference betweenthe selected reference pixels; a prediction waveform informationgeneration unit to generate prediction waveform information based on thereference block waveform information and a value of the standard pixel;and a coding unit to code an image included in the target image blockbased on the prediction waveform information and a pixel value of codingpixels included in the target image block.

INDUSTRIAL APPLICABILITY

According to the present invention, it is possible to reduce a size of acoded image and to improve a quality of the coded image by effectivelycoding an input image.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a structure of an apparatus forcoding a moving image according to conventional technologies;

FIG. 2 is a block diagram illustrating a structure of an apparatus forcoding an image according to an exemplary embodiment of the presentinvention;

FIG. 3 is a diagram illustrating a direction of a reference blockwaveform according to an exemplary embodiment of the present invention;

FIG. 4 is a diagram illustrating a conventional method for coding atarget image based on a pixel value of a standard pixel included in areference image block;

FIG. 5 is a diagram illustrating an exemplary embodiment of the presentinvention which codes a target image block based on waveform informationof a reference image block;

FIG. 6 is a block diagram illustrating a structure of an apparatus fordecoding an image according to an exemplary embodiment of the presentinvention; and

FIG. 7 is a block diagram illustrating a structure of an apparatus forcoding an image according to an exemplary embodiment of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, exemplary embodiments of the present invention will bedescribed in detail by referring to accompanied drawings.

FIG. 2 is a block diagram illustrating a structure of an apparatus forcoding an image according to an exemplary embodiment of the presentinvention. Hereinafter, operations of the apparatus 200 for coding theimage according to the exemplary embodiment of the present inventionwill be described with reference to FIG. 2. The apparatus 200 for codingthe image according to the exemplary embodiment of the present inventionmay include an input image segmentation unit 210, a waveform informationgeneration unit 220, and a coding unit 230.

The input image segmentation unit 210 segments input images into aplurality of image blocks. A first image block and a second image blockare included in the plurality of image blocks.

The waveform information generation unit 220 may generate first waveforminformation about the first image block and second waveform informationabout the second image block. The waveform information generation unit220 may select a plurality of pixels among pixels included in the firstimage block and generate the first waveform information about the firstimage block based on differences between pixel values from the selectedplurality of pixels. The waveform information generation unit 220 maygenerate the second waveform information about the second image blockbased on the differences between pixel values from the second imageblock.

Waveform information may include pixel value differences from theplurality of pixels included in an identical image block. In otherwords, among the plurality of pixels included in the first image block,the difference in the pixel value from the first pixel and the secondpixel selected may be included. An apparatus for decoding an image whichdecodes the second image block by referring to the first image block maycalculate the pixel value differences in the pixels included in thefirst image block by referring to the waveform information of the firstimage block, and decode the second image block based on the calculatedpixel value differences. Since the distance between the first pixel andthe second pixel in the first image block may be easily calculated, andinclination related to the first and the second pixel value also may beeasily calculated. According to the present invention, the apparatus fordecoding the image which decodes the second image block may decode thesecond image block by determining that the inclination related to thepixel values in the plurality of pixels included in the second imageblock is similar to the inclination related to the pixel values in theplurality of pixels included in the first image block.

The waveform information generation unit 220 may additionally select athird pixel included in the first image block, and waveform mayadditionally include a pixel value difference from the second pixel andthe third pixel. In such case, the first waveform information about thefirst image block may include the pixel value differences with respectto three pixels. In this instance, the inclination related with thepixel value differences for the first pixel and the second pixel isgenerally different from the inclination related with the pixel valuedifferences for the second pixel and the third pixel.

According to an exemplary embodiment of the present invention, thesecond image block may include a fourth pixel, a fifth pixel, and asixth pixel which correspond to the first pixel, the second pixel, andthe third pixel included in the first block respectively. The apparatusfor decoding the image which decodes the second image block determinesthe pixel value for the fourth pixel, the fifth pixel, and the sixthpixel by referring to the inclination related with the first pixel, thesecond pixel, and the third pixel.

The first block and the second block may be adjacent image blocks.

The second image block is coded based on the first image block.Therefore, in order to decode the second image, information regardingthe first image block is required. Since the input image is segmentedinto a plurality of image blocks, in order to decode the second imageblock, the first image block is required to be identified. According toan exemplary embodiment of the present invention, the second waveforminformation may include location information of the first image blockwith respect to the second image block and the decoding apparatus canidentify the first image block from the location information of thefirst image block with respect to the second image block. The apparatusfor decoding the image may decode the second image block based on theidentified first image block.

According to an exemplary embodiment of the present invention, thewaveform information generation unit 220 may generate the first waveforminformation about the first image block by selecting a plurality ofpixels which are adjacent to each other among the pixels included in thefirst image block.

According to an exemplary embodiment of the present invention, thewaveform information generation unit 220 may generate the first waveforminformation about the first image block by selecting a plurality ofpixels according to a predetermined direction among the pixels includedin the first image block.

The coding unit 230 may code an image included in the first image blockbased on differences between the first waveform information and thesecond waveform information. According to an exemplary embodiment of thepresent invention, the first waveform information may includeinformation about a predetermined direction in which the plurality ofpixels in the first image block are selected, and the coding unit 230may code an image included in the second image block based on thedirection information of the selected direction in the plurality ofpixels of the first image block.

FIG. 3 is a diagram illustrating a direction of a reference blockwaveforms according to an exemplary embodiment of the present invention.Hereinafter, directions of reference block waveforms according to theexemplary embodiment of the present invention will be described withreference to FIG. 3.

According to an exemplary embodiment of the present invention, thewaveform information generation unit 220 of FIG. 2 may select aplurality of pixels according to a predetermined direction within thefirst image block. According to an exemplary embodiment of the presentinvention, the waveform information generation unit 220 may determine animage prediction mode for the first image block, and also determinedirections to select the plurality of pixels according to the determinedimage prediction mode.

In FIG. 3, an image prediction mode 0 is an image prediction mode whichselects vertical pixels in the plurality of pixels included in the firstimage block.

An image prediction mode 1 is an image prediction mode which selectshorizontal pixels in the plurality of pixels included in the first imageblock.

An image prediction mode 3 is an image prediction mode which selectspixels of a diagonal downward left direction in the plurality of pixelsincluded in the first image block.

An image prediction mode 4 is an image prediction mode which selectspixels of a diagonal downward right direction in the plurality of pixelsincluded in the first image block.

An image prediction mode 5 is an image prediction mode which selectspixels of a vertical rightward direction in the plurality of pixelsincluded in the first image block.

An image prediction mode 6 is an image prediction mode which selectspixels of a horizontal downward direction in the plurality of pixelsincluded in the first image block.

An image prediction mode 7 is an image prediction mode which selectspixels of a vertical leftward direction in the plurality of pixelsincluded in the first image block.

An image prediction mode 8 is an image prediction mode which selectspixels of a horizontal upward direction in the plurality of pixelsincluded in the first image block.

An image prediction mode 2 is an image prediction mode which selects allpixels in the plurality of pixels included in the first image block.

According to an exemplary embodiment of the present invention, the firstwaveform information generated from the waveform information generationunit 220 may include the information about the predetermined directionin which the plurality of pixels in the first image block are selected.According to an exemplary embodiment of the present invention, the firstwaveform information may include the image prediction mode whichcorresponds to the predetermined direction of the plurality of pixels inthe first image block being selected. The apparatus for decoding theimage which decodes the image included in the second image block mayobtain direction information about the plurality of pixels in the firstimage block, by referring to the information of the image predictionmode of the first image block. The apparatus for decoding the image maydecode an image included in the second image block by referring to thedirection information about the predetermined direction of the pluralityof pixels of the first image block being selected.

FIG. 4 is a diagram illustrating a conventional method for coding atarget image block 430 based on a pixel value of a standard pixelincluded in a reference image block 410.

According to the conventional method for coding the target image, asingle standard pixel is selected in a plurality of pixels 411, 412,413, and 414 which are included in a reference image block 410.According to an exemplary embodiment of the conventional method, a pixeladjacent to the target image block 430 or a pixel closest to the targetimage block 430 may be selected as a standard pixel.

According to the conventional coding method, a prediction value 440 forpixels 431, 432, 433, and 434 which are included in the target imageblock 430 is performed using only one pixel 414 from among the pixelsincluded in the reference image block 410, and coding is performed withrespect to value difference between the predicted value 440 and theactual pixels 431, 432, 433, and 434. According to the conventionalmethod, in the case the prediction is performed with respect to pixels431, 432, 433, and 434 included in the target image block 430exclusively using the single pixel 414, this may result inaccuratepredicted values. Consequently, the conventional method may effectivelycode the target image block 430.

FIG. 5 is a diagram illustrating an exemplary embodiment of the presentinvention which codes a target image block based on waveform informationof a reference image block. Hereinafter, exemplary embodiments of thepresent invention will be described with reference to FIG. 5. FIG. 5illustrates an exemplary embodiment that a reference image block isadjacent to a target image block. However, in another exemplaryembodiment of the present invention, a reference image block may not beadjacent to a target image block.

An apparatus for coding an image according to an exemplary embodiment ofthe present invention may generate waveform information of a referenceblock 520 using pixel values of a plurality of pixels 511, 512, 513, and514 included in a reference image block 510. According to an exemplaryembodiment of the present invention, the reference block waveforminformation 520 may include information about value differences betweenthe plurality of pixels 511, 512, 513, and 514 which are included in thereference image block 510.

In general, a size of the reference image block 510 or of the targetimage block 530 is 4×4 or 16×16. The target image to be coded issegmented into plurality of image blocks before being coded. Theadjacent image blocks may include similar images. Each of the imageblocks having similar images may include a plurality of pixels withsimilar patterns.

In the case pixels 511, 512, 513, and 514 of the reference image block510 have similar patterns 520 and 521, the reference block waveforminformation 520 which connects values of the plurality of pixels 511,512, 513, and 514 included in the reference image block 510 is similarto the target block waveform information 550 which connects values ofthe plurality of pixels 531, 532, 533, and 534 of the target image block530.

Consequently, it is possible to code the target image block 530 based onthe reference block waveform information 520 which includes values ofthe plurality of pixels 511, 512, 513, and 514 included in the referenceimage block 510, as well as based on a value of the standard pixel 514included in the reference image block 510.

The apparatus for coding the image according to an exemplary embodimentof the present invention may generate prediction waveform information540 about the target image block 530 using the reference block waveforminformation 520. According to an exemplary embodiment of the presentinvention, the apparatus for coding the image may generate theprediction waveform information 540 using the value differenceinformation between the plurality of pixels 511, 512, 513, and 514included in the reference image block 510.

The apparatus for coding the image may generate the reference blockwaveform information 521 exclusively using a portion of pixels 511, 512,513, and 514 included in the reference image block 510. The apparatusfor coding the image may also generate reference block waveforminformation 521 exclusively using a first pixel 511 and a last pixel 514from among the reference image block 510. In the case the referenceblock waveform information 521 is generated in a simplified way byexclusively using the portion of pixels, a load of calculation may bereduced.

The apparatus for coding the image according to an exemplary embodimentof the present invention may select the standard pixel 514 from amongthe plurality of pixels 511, 512, 513 and 514 included in the referenceimage block 510, determine the prediction waveform information 540 basedon the pixel value of the standard pixel 514. According to an exemplaryembodiment of the present invention, it is possible to determine thepixel value of the first prediction pixel 541 by referring to the pixelvalue of the standard pixel 514 from among the plurality of predictionpixel values 541, 542, 543, and 544 included in the prediction waveforminformation 540.

Since the reference block waveform information 521 includes informationregarding relative pixel differences among the plurality of pixels 511,512, 513, and 514 included in the reference image block 510, theapparatus for coding the image may determine the plurality of predictionpixel values of 541, 542 543, and 544 included in the predictionwaveform information 540 by referring to the pixel value of the standardpixel 514.

According to an exemplary embodiment of the present invention, theapparatus for coding the image may determine either a closest pixel oran adjacent pixel to the target image block 530 from among the pluralityof pixels 511, 512, 513, and 514 included in the reference image block510 as the standard pixel 514. The closest pixel to the target imageblock 530 or the adjacent pixel 514 to the target image block 530 tendsto have a small difference value from pixel values of the target imageblock 530 in general. Consequently, there are small differences betweenthe prediction waveform information 540 and the plurality of pixels 531,532, 533, and 534 included in the actual target image block 530.

The apparatus for coding the image according to an exemplary embodimentof the present invention is capable of coding value differences 551,552, 553, and 554 between the plurality of pixels included in the targetimage block 530 and the prediction waveform information 541, 542, 543,and 544 corresponding to each of the pixels.

A range of possible values in the value differences 551, 552, 553, and554 between the plurality of values 531, 532, 533, and 534 included inthe target image block 530 and prediction waveform information 541, 542,543, and 544 is smaller than a range of possible values in the pluralityof possible pixels 531, 532, 533, and 544 included in the target imageblock 530. Also, the range of possible values in the value differences551, 552, 553, and 554 between the plurality of pixel values 531, 532,533, and 534 of the target image block 530 and prediction waveforminformation 541, 542, 543 and 544 is smaller than the range of possiblevalues in the value differences of a pixel value of the standard pixel514 and the plurality of pixel values 531, 532, 533, and 534.

Consequently, according to the present invention, it is possible to codea specific pixel using a smaller amount of bits. Also, with a sameamount of bits, it is possible to code the specific pixel to a betterquality. Since a size of the coded image decreases, transmission in bothwired and wireless communication becomes more convenient.

FIG. 5 illustrates an exemplary embodiment that the standard pixel isincluded in the reference image block. However, according to anotherexemplary embodiment of the present invention, a standard pixel may beincluded in a target image block as well. According to an exemplaryembodiment of the present invention, a pixel in the target image block,which is located in a boundary toward the reference image block, may beselected as the standard pixel. In such case, a pixel value differencebetween the standard pixel and the prediction waveform information isnot coded, but a pixel value of the standard pixel is coded.

Also, FIG. 5 illustrates an exemplary embodiment that only fourreference pixels are selected among the pixels in the four referenceimage blocks 510, yet in another exemplary embodiment of the presentinvention, it is possible to select more than 4 pixels for referencepixels to generate prediction waveform information.

FIG. 6 is a block diagram illustrating a structure of an apparatus 600for decoding an image according to an exemplary embodiment of thepresent invention. The apparatus 600 for decoding the image according toan exemplary embodiment of the present invention may include a referenceblock waveform information generation unit 610, a prediction pixel valuegeneration unit 620, and a coding unit 630.

The reference block waveform information generation unit 610 maygenerate reference block waveform information based on pixel valuedifferences of reference pixels included in the reference image block.The reference block waveform information generation unit 610 accordingto an exemplary embodiment of the present invention may select pixelswhich are arranged to a predetermined direction among the referencepixels included in the reference image block, and generate referencewaveform information based on the value differences between the selectedpixels. According to an exemplary embodiment of the present invention,the reference block waveform information generation unit 610 maygenerate reference block waveform information by comparing pixel valuesof pixels which are adjacent with each other from among the selectedpixels. Since all of the selected pixels are used in generation ofreference block waveform information, the generated reference blockwaveform information is highly accurate.

According to another exemplary embodiment of the present invention, thereference block waveform information generation unit 610 may generatereference block waveform information by exclusively comparing pixelvalues of only a portion of pixels from among the selected pixels. Sinceonly the portion of pixels is used in the generation of the referenceblock waveform information, the reference block waveform information maybe easily generated. According to an exemplary embodiment of the presentinvention, the reference block waveform information generation unit 610may generate the reference block waveform information exclusively usingthe first pixel and the last pixel from among the selected pixels.

The prediction pixel value generation unit 620 may generate predictionpixel value based on a pixel value of a standard pixel within thereference block waveform information or the reference image block. Thereference block waveform information only includes information about apixel value difference between selected pixels. Consequently,information such as whether the first pixel value is smaller than thesecond pixel value may be included in the reference block waveforminformation, however information of an exact value of the first pixelvalue may not be included in the reference block waveform information.

The prediction pixel value generation unit 620 may generate a predictionpixel value based on a pixel value of a standard pixel. According to anexemplary embodiment of the present invention, the standard pixel may beselected among the selected reference pixels. According to an exemplaryembodiment of the present invention, among the selected referencepixels, a pixel closest to a target image block or a pixel adjacent to areference image block may be selected as a standard pixel. According toan exemplary embodiment of the present invention, among the selectedreference pixels, a pixel located in a boundary toward the target imageblock may be selected as the standard pixel. The prediction pixel valuegeneration unit 620 may generate a prediction pixel value by referringto the location information of the selected standard pixel.

According to an exemplary embodiment of the present invention, theprediction pixel value generation unit 620 may select the standard pixelfrom pixels of the target image block.

According to an exemplary embodiment of the present invention, theprediction pixel value generation unit 620, among the plurality ofpixels included in the target image block, may determine a pixel valueof a pixel which is closest to the reference image block to be identicalto a pixel value of a standard pixel. Also, the prediction pixel valuegeneration unit 620 may generate prediction pixel values whichcorrespond to each of the pixels of the target image block. Connectingeach of the prediction pixel values would result generation ofprediction waveform information. According to an exemplary embodiment ofthe present invention, the prediction pixel value generation unit 620may determine the prediction pixel value so that a form of theprediction waveform information is identical to a form of the referenceblock waveform information.

The decoding unit 630 may decode an image included in the target imageblock based on the prediction pixel values. According to an exemplaryembodiment of the present invention, the decoding unit 630 may calculatedecoding data values for the target image block, add the calculateddecoding data values and prediction pixel values, and decode the imageincluded in the target image block.

The reference image block and the target image block may be image blocksadjacent to each other, however, according to another exemplaryembodiment of the present invention, a reference image block and atarget image block may also not be adjacent.

The apparatus for coding the image may code only differences between thepixel values of pixels included in the target image block and predictionpixels, and the decoding unit 630 may calculate an accurate value ofpixels included in the target image block based on the prediction pixelvalues.

A range of a difference between the pixel values of pixels included inthe target image block and the prediction pixel value is smaller than arange of the values of pixels included in the target image block.Consequently, coding of the differences between the values of pixelsincluded in the target image block and the prediction pixel values mayimprove overall effectiveness in coding of an input image, compared tothe case of coding with the pixel values from the target image blockalone.

According to the present invention, it is possible to code/decode inputimages using a fewer number of bits than the conventional technology. Itis also possible to code/decode images with higher quality using a samenumber of bits as the conventional art. Since a size of the coded imageis reduced, transmissions via both wired and wireless networks may beeasy.

According to an exemplary embodiment of the present invention, theprediction pixel value generation 620 may generate a prediction pixelvalue based on a direction of the reference image block in relation tothe target image block. According to an exemplary embodiment of thepresent invention, in the case the reference block is located in anupper direction, a prediction mode for the prediction image block may be‘0’. In the case a prediction mode for a prediction image block is ‘0’,the apparatus for coding the image may generate the reference blockwaveform information by selecting reference pixels which are verticalfrom among the reference pixels in the reference image block. Thedirection of the selected reference pixels is identical to a directionof the target image block from the reference image block. The predictionpixel value generation unit 620 may generate prediction pixel values forimage pixels whose direction is identical to that of the selectedreference pixels, from among the image pixels included in the referenceimage block. In the case the direction of the selected reference pixelsis identical to the direction of the prediction pixels, a deviationbetween pixel values of the selected reference pixels and the predictionpixel values may be minimized.

FIG. 7 is a block diagram illustrating a structure of an apparatus forcoding an image according to an exemplary embodiment of the presentinvention. The apparatus for coding the image according to an exemplaryembodiment of the present invention may include an input imagesegmentation unit 710, a reference block waveform information generationunit 720, and a prediction waveform information generation unit 730, anda coding unit 740.

The input image segmentation unit 710 may segment an input image into aplurality of blocks which includes a reference image block or a targetimage block. According to an exemplary embodiment of the presentinvention, the reference image block and target image block may be imageblocks adjacent to each other. However, the reference image block andtarget image block may not be adjacent to each other according toanother exemplary embodiment of the present invention.

The reference block waveform information generation unit 720 may selectthe plurality of reference pixels from among pixels included in thereference image block, and generate reference block waveform informationbased on pixel value differences between the selected reference pixels.The generated reference block waveform information only includesinformation about a relative difference in pixel values between thereference pixels.

According to an exemplary embodiment of the present invention, thereference block waveform information generation unit 720 may generatereference block waveform information based on the pixel valuedifferences of reference pixels adjacent to each other. Since allreference pixels included in the reference image block are used in thegeneration of the reference block waveform information, it is possibleto generate more accurate waveform information. In another exemplaryembodiment of the present invention, the reference block waveforminformation generation unit 720 may also generate reference blockwaveform information using only a portion of reference pixels from theselected reference pixels. In this instance, since the reference blockwaveform information generation unit 720 generates the reference blockwaveform information in a simplified way, a computational loaddecreases.

The prediction waveform information generation unit 730 may generateprediction waveform information based on a standard pixel value includedin the reference block waveform information and reference image block.The standard pixel value is a pixel value of a standard pixel includedin the reference image block. According to an exemplary embodiment ofthe present invention, the prediction waveform information generationunit 730 may select the standard pixel using a pixel adjacent to atarget image block from among all pixels included in the reference imageblock. Also, the prediction waveform information generation unit 730 mayselect a pixel, which is located in a boundary toward the target imageblock from among all pixels included in the reference image block, asthe standard pixel.

When the pixel, which is located in a boundary toward the target imageblock, is selected from among all pixels included in the reference imageblock, the prediction waveform information generation unit 730 maydetermine a pixel value of the standard pixel as a starting value of theprediction waveform information. Since a distance between the standardpixel and the target image block is significantly close, pixel valuedifferences between pixels included in the target image block and thestandard pixel are significantly small. Thus, it is possible toeffectively code the target image block.

According to an exemplary embodiment of the present invention, in thecase the reference block and the target image block are not adjacent toeach other, the prediction waveform information generation 730 maygenerate prediction waveform information based on the distance from thereference image block to the target image block. According to anexemplary embodiment of the present invention, the prediction waveforminformation generation 730 may calculate an inclination value of thereference block waveform information, and also may obtain a startingvalue of the prediction waveform information based on the calculatedinclination value. The prediction waveform information generation unit730 may generate the prediction waveform information based on relativepixel value differences between the starting value of the predictionwaveform information and the pixel value of the reference pixel.

According to an exemplary embodiment of the present invention, thereference block waveform information generation unit 720 may select theplurality of reference pixels according to a predetermined direction,and the prediction waveform information generation unit 730 may generatethe prediction waveform information based on the predetermined directionin which the reference pixels are selected. According to an exemplaryembodiment of the present invention, the reference block waveforminformation generation unit 720 may determine the predetermineddirection in which the reference pixels are selected based on adirection of the target image block from the reference image block.

The coding unit 740 may code an image included in the target image blockbased on a pixel value of coding pixels included in the predictionwaveform information and the target image block. According to anexemplary embodiment of the present invention, the coding unit 740 maycode a pixel difference between the coding pixels included in theprediction waveform information and the target image block.

Although the present invention has been described in connection with theembodiment of the present invention illustrated in the accompanyingdrawings, it is not limited thereto since it will be apparent to thoseskilled in the art that various substitutions, modifications and changesmay be made thereto without departing from the scope and spirit of theinvention.

Therefore, it is intended that the scope of the invention be defined bythe claims appended thereto and their equivalents.

What is claimed is:
 1. A method for decoding an image, the methodcomprising: generating waveform information that represents differencesin pixel values between pixels of a predetermined direction neighboringa target image block; generating prediction pixel values for pixels inthe target image block based on the waveform information; and outputtingpixel values of the pixels in the target image block based on theprediction pixel values, wherein the pixels of the predetermineddirection neighboring the target image block are selected from referenceimage blocks neighboring the target image block, and the generating ofthe prediction pixel values for pixels in the target image blockcomprises generating the prediction pixel values for pixels in thetarget image block that are adjacent to predetermined reference pixelsamong the pixels of the predetermined direction neighboring the targetimage block.
 2. The method of claim 1, wherein the outputting of thepixel values of the pixels in the target image block comprises decodingthe target image block by adding each of the prediction pixel values toa coding data value for a respective pixel of the target image block toobtain a pixel value of the respective pixel of the target image block.3. The method of claim 1, wherein the waveform information is generatedbased on pixels that are adjacent to the target image block among thepixels of the predetermined direction neighboring the target imageblock.